A good general rule when compiling for a sparc box is to "start from scratch" somewhat with the kernel ...

overlooking seemingly innocent drivers, like some of the you-wont-need-it network stuff or firewire drivers or whatever, can cause a sparc kernel to fail compilation very quickly.

When I got my first sparc and threw gentoo at it, it took me about 5 or 6 passes through make menuconfig to finally get all the trash out and make the kernel build ok.

I want to second that, Ligthert, and suggest that you fall back and punt (if you're a football kind of guy) and use the sparc kernel sources first. I know they're 2.4.x but they work much more gooderly out of the box than trying to sparc-ize the 2.6 kernels. After getting my Ultra10 up and running 2.4.29, I spent three days going through the 2.6 menuconfig (well, not really three WHOLE days, but three evenings - as much as my lovely wife would allow) making sure I had deleted everything I didn't need and adding in only what I did need to get the first 2.6 kernel boot. Once I got it to boot the first time (what a pleasant surprise THAT was!), I went back through and added drivers and framebuffers one at a time so i could back out quickly if I made a teensy tiny mistake.